A new report, published as part of the Scottish Government's drive to detect cancers as early as possible, has revealed an increase of 4.7 per cent in the number of cases of breast, lung, and bowel cancers diagnosed at stage one.
Most mainland health boards have reported an improvement, but four show a reduction - NHS Highland, NHS Borders, NHS Dumfries and Galloway and NHS Forth Valley.
NHS Borders has seen a drop of 24.8 per cent in the proportion of the three cancers combined detected at stage one, the largest decrease in Scotland.
The report, published by the Information Services Division (ISD) of NHS Scotland yesterday, said: "This may be due, in some part, to the breast screening mobile unit not visiting during all of 2012 and only from August 2013 onwards."
Women between the ages of 50 and 70 are offered mammograms approximately every three years to check for signs of breast cancer. The screening programme is run from six centres, and they send mobile units to outlying areas to check the eligible population in line with this schedule.
ISD said that, as the screening unit had not been due to visit the Borders for most of the last two years, it may explain why a smaller proportion of breast cancers had been picked up at stage one.
NHS Shetland had the lowest proportion of breast cancers diagnosed at stage one at 27.9 per cent during 2012 and 2013. The ISD report also said this "may be due, to some extent, to the breast screening mobile unit not visiting the island during 2012".
The proportion of patients whose breast cancer was detected at stage one in 2012-13 varied among mainland health boards from 29.7 per cent in NHS Borders to 43.8 per cent in NHS Highland.
James Jopling, Scotland director at Breakthrough Breast Cancer, said the charity welcomed the Detect Cancer Early initiative.
He said: "We were particularly encouraged when, after a period of activity highlighting breast cancer, GPs reported a significant rise in the number of women making appointments to check out concerns over potential signs and symptoms.
"However, it is frustrating that these figures do not provide a consistent picture of stage one diagnosis rates for breast cancer across Scotland due in part to normal variations in the areas the screening programme visits.
"Detect Cancer Early is currently running a campaign to improve attendance at breast screening. To get a true sense of how successful the overall initiative has been for breast cancer we will have to wait until all activity to improve early detection has ended."
The first wave of the Scottish Government's drive to detect more cancers early included a high-profile advertising campaign featuring actress Elaine C Smith. It prompted a significant rise in the number of women seeking advice.
Some of the improvement in the number of cancers caught early is due to better data capture, including a reduction in the number of cancers for which no stage was known, according to officials.
Health Secretary Alex Neil said: "When it comes to cancer we will always fight for more because even more lives can be saved in Scotland through earlier detection. Health boards must continue to target specific communities to encourage more Scots to get checked early."